Landfills are commonly used to dispose of waste materials of many different types. These waste materials can include paper products, food scraps, yard waste, metal, glass, plastic and a host of other materials. In an attempt to reduce the amount of waste material that is deposited in landfills, source separating efforts in the form of recycling programs have been instituted. To the extent they are used, such recycling programs help reduce landfill dependence. However, it has been found that such recycling programs only result in the removal of a relatively small percentage of the total waste material. In the case of at least some material, such as paper products and others, the relatively small recovery rate can be attributed at least in part to the fact that a large percentage of the products are food-contaminated and thus quite difficult to separate and recycle.
Various proposals have been made in the past to treat waste material prior to its introduction into a landfill in an attempt to recover portions of the material and thereby reduce landfill dependence. However, generally speaking, those proposals have not been well received as they are not particularly suited for efficiently and effectively treating different types of waste materials such as those commonly found in municipal solid waste. Municipal solid waste is generally the most complex and mixed material occurring in waste streams. Thus, systems for effectively and efficiently treating municipal solid waste must be capable of treating and breaking down a wide range of different materials.
In addition to being not well suited for handling a wide range of materials, past proposals for treating waste material also suffer from other disadvantages and drawbacks. For example, some proposals require a supply of heated boiler quality water for heating the material being treated. The need for water of that quality significantly increases the cost and complexity of the treating facility. Moreover, the use of boiler quality water is quite needless since the water immediately becomes contaminated once it is introduced into the material being treated.
In addition, in situations in which the material being treated has been heated and saturated with hot water for purposes of breaking down the waste material, steam is employed in an attempt to dry the material to a specified degree. However, as might be expected, steam is not very well suited as a drying mechanism since it tends to introduce additional moisture into the material. Thus, past proposals have not been well suited to allowing the material to be dried to any desired degree. Moreover, little effort is made to recover the heat that is generated during the treatment process.